docs: def add_arguments(parser):
      """
         Parse arguments
         Args:
             parser (argparse.ArgumentParser)
         """
      parser.description = 'Examples:\n' \
                           'python -m etk regex_extractor pattern /tmp/date.txt\n' \
                           'cat /tmp/date.txt | python -m etk regex_extractor pattern'
      parser.add_argument('pattern', nargs='?', type=str, default=sys.stdin)
      parser.add_argument('input_file', nargs='?', type=argparse.FileType('r'), default=sys.stdin)